When manufacturing a product, it is important that the resulting product is reliable and that little waste is generated in the manufacturing process. When manufacturing integrated circuits, it is important to ensure that elements of the integrated circuit are functioning properly. Therefore, integrated circuits are typically tested to determine whether they are functioning properly before they are shipped. Depending upon the results of the testing, the integrated circuits may be categorized according to certain performance criteria, such as the speed of the device for example. An integrated circuit may even be discarded if a certain number of defects are found in the integrated circuit. For example, if more than two defective memory cells are found in a block of random access memory, the integrated circuit may be discarded. Discarding defective integrated circuits decreases the yield of a batch of wafers, thereby affecting the overall cost of manufacturing the integrated circuits. Accordingly, there is always an effort in the manufacture of integrated circuits to improve the yield.
Memory cells are one element of an integrated circuit which may be determined to be defective. Although redundant memory cells may be selected if a memory cell is determined to be defective in order to improve yield, the amount of circuitry required to improve the yield may be prohibitive. That is, the amount of circuitry needed to compensate for defective memory cells may significantly reduce the available memory or the area for other circuitry in a die.